Oksidacijsko ponašanje modernih višefaznih konstrukcijskih čelika pri visokim temperaturama

master's thesis

• Title (english): Oxidation behavior of advanced multiphase structural steels at high temperatures
• Author: Desimir Bobinac
• Mentor: Anita Begić Hadžipašić (mentor)
• Committee member: Damir Hršak (predsjednik povjerenstva)
• Committee member: Anita Begić Hadžipašić (član povjerenstva)
• Committee member: Stjepan Kožuh (član povjerenstva)
• Granter: University of Zagreb; Faculty of Metallurgy; Sisak
• Defense date and country: 2017-09-29, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Metallurgy

Abstract

U ovom radu ispitano je oksidacijsko ponašanje višefaznih konstrukcijskih čelika pri T = 650 oC, kao i korozijska otpornost u 3,5% otopini NaCl termički tretiranih uzoraka. Elektrokemijska mjerenja su pokazala da termički tretirani uzorci poprimaju pozitivniji korozijski potencijal i pokazuju manju brzinu korozije od termički netretiranih uzoraka. Analizom EIS – spektara ustanovljeno je da termički tretirani uzorci pokazuju veći otpor prijenosu naboja, što znači da nastali oksidni sloj ima zaštitnu ulogu u korozijskom procesu i dovodi do smanjenja brzine korozije. Metalografska ispitivanja su pokazala da su ispitani konstrukcijski čelici izrazito sitnozrnate mikrostrukture koja se sastoji od ferita, bainita i zaostalog austenita. Manji sadržaj zaostalog austenita po granicama zrna kod uzoraka J i K doveo je do bolje korozijske otpornosti u 3,5% otopini NaCl, budući da su mogućnosti za formiranje korozijskih članaka bitno smanjene.

Abstract (english)

In this paper oxidation behavior of advanced multiphase structural steels at T = 650 oC was studied, so as corrosion resistance in 3,5% NaCl solution of heat treated samples. Electrochemical measurements have shown that heat treated samples adopt more positive
corrosion potentials and show lower corrosion rate than not heat treated samples. By analisys of EIS spectrum was found that heat reated samples have higher charge transfer resistance which means that formed oxide layers have protective role in corrosion process leading to decrease in corrosion rate. Metallographic examinations have shown that samples have very fine grain microstructure consisted of ferrite, bainite and residual austenite. Residual austenite situated at grain boundaries in samples J and K lead to better corrosion resistance in 3,5% NaCl solution because the probabilities of formation of local galvanic cells were decreased.

• Keywords: TRIP – čelici; visokotemperaturna korozija; brzina korozije; elektrokemijska ispitivanja; mikrostruktura
• Keywords (english): TRIP – steels; high temperature corrosion; corrosion rate; electrochemical measurements; microstructure
• Language: croatian
• URN:NBN: urn:nbn:hr:115:837043
• Study programme: Title: Graduate study program Metallurgy; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka metalurgije (magistar/magistra inženjer/inženjerka metalurgije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2017-10-24 06:37:46